Rear turbine stabilized helicopter, the so-called "Notartype", are a new generation of helicopters which are characterized by the use of an internal turbine-like mechanism in the tail section of the craft to steer and stabilize the craft. The turbine replaces the traditional rear external blade (so-called "tail rotor") which heretofore has caused numerous spin-outs and fatal crashes.
The rear turbine comprises a housing having a plurality of air foil blade assemblies arranged therein to form a turbine or fan-like device in the tail section of the air craft. In theory, the placement of a blade turbine in the tail assembly and the venting of the combustion gases from the prime motor through that turbine to counteract the torque of the main rotor proved sound. In practice, however, it was not reliable because the air foil blades had to be hand made and were constructed of a hand laminated fiberglass covering which was disposed upon a rubber core. This construction disintegrated on use and caused the pilot to lose the degree of aircraft control needed for safe flight. In addition, the discrepancies between hand crafted blades created an extraordinary high percentage of rejects.
As indicated above, the prior art air foil blades were produced by telescopically disposing a blade in the end of a metal spar and thereafter covering the assemblage by a hand lay-up process in which layers of woven material, such as laminated fiberglass, were laid over and around the structure. The laminate was thereafter impregnated with an epoxy adhesive, baked, and trimmed.
Another prior art attempt to make an improved air foil blade utilized a rubber mandrel covered with a plurality of layers of nylon mesh. The layers of nylon mesh were then epoxy coated, placed into a mold, and the entire mold was thereafter baked in an autoclave. The baked article was then split open on three sides to form a clothes pin-like member from which the rubber mandrel was removed. Next, epoxy was placed into the resulting shell and the epoxy filled member was then baked in an autoclave. The baking caused the epoxy to expand within the shell and form a foam core. The resulting blade was then balanced, sanded, shaped and painted.
Blades produced in this fashion were also found to be extremely unreliable because they would easily delaminate when chipped and would totally self destruct when such delamination was allowed to progress undetected. Delamination of any degree creates blade imbalance and erratic performance of the craft in which they were used. Further, air foil blades made in this fashion were so labor-intensive and the cost so high that only the government could afford to purchase them.
It is toward the solution of these prior art air foil blade problems by providing a novel and unique blade which enhances the reliability and safety of the aircraft in which it is used while substantially reducing of the unit cost of each blade that the present invention is directed.